The present invention relates to receive circuits for ultrasound imaging. In particular, receive circuits for use with different transducers are provided.
Ultrasound imaging for echocardiography applications requires transducers with high volume-per-second rates for scanning. For real-time imaging of moving structures, 20 or more, such as 35, two or three-dimensional representations are generated each second. Large amounts of information are communicated from an ultrasound probe to an ultrasound system base unit.
Various transducers and associated beamformers have been provided for three-dimensional ultrasound imaging. Currently, mostly mechanical transducers are used. However, the associated imaging is not provided in real time and typically requires ECG gating. Two-dimensional transducer arrays for faster electronic/electronic steering and volume acquisition also have been provided. For example, sparse two-dimensional arrays or fully sampled two-dimensional arrays have been used. Sparse arrays provide poor contrast resolution.
Fully sampled two-dimensional arrays use expensive additional beamforming hardware. Two-dimensional arrays repetitively generate transmit beams and responsive receive beams. The beams are electronically steered within the three-dimensional volume. Electronic steering requires a system channel for each of the elements used. Since the number of elements in a two-dimensional array is high, the number of channels required is high. More channels require a greater number of cables. Providing beamforming or partial beamforming within the probe of the transducer array may reduce the number of cables required, but the required number of channels and hardware for sampling the two-dimensional array is still high. Furthermore, analog delays used for beamforming in the probe are expensive and large, and the beamformer in the probe may have limited programmability.
Transducer arrays include elements with a ground electrode and a signal electrode switchably connected to separate transmit and receive system channels. With beamforming capabilities built into the probe, high voltage transistors or diodes operating as switches to isolate the transmit channels from the receive channels are also included within the probe. These high voltage devices are not easily integrated with the beamforming circuitry, so require additional space.
In one system disclosed in U.S. Pat. No. 5,622,177, the number of system channels and cables is reduced by using time division multiplexing. Data from a plurality of elements is multiplexed onto one signal line. However, time division multiplexed data has different characteristics than conventional data representing the signal from a single transducer element. Receive circuitry designed for use with conventional data may improperly introduce noise or errors in time division multiplexed data.